Investigations are directed at the mechanisms controlling differentiation of lymphoid and plasma cells, and of immunoglobulin gene expression, mRNA metabolism and polypeptide chain synthesis assembly and secretion (or insertion into membrane). Lymphoid cell membranes are investigated for antigen receptors, antibody (Fc) receptors and HL-A antigens. Antigens characteristic of stages of lymphoid cell class and differentiation as well as tumor associated antigens are sought. The structural relationships and metabolic features of these molecules are being determined. Humoral and immune cell interrelationship in response to allogeneic and syngeneic tumors are being defined. Specific immune functions assessed in vitro are related to graft and tumor survival (or rejection) in vivo. The biologic effects of modified antigens and cell surfaces are being explored. Immunologic evaluations of B and T lymphoid cell and macrophage function are being made in man during health and disease. These parameters are also evaluated during attempts at therapy. Immunology of human tumors is under study with efforts to detect tumor associated antigens and specific immune response. Immunotherapy for human disease is being explored in preclinical models in preparation for adjunctive and specific manipulations of immune response in man. Bone marrow transplantation is being used in patients with neoplasma or with aplastic anemia. Animal systems are being developed for new approaches to the control of GvH disease.